Bump/Lump on the Face

Hi guys I don't have pictures so I'm going to try and describe this in my very non-english, creative writing background that I don't have.
Yesterday I put Jessie and Gunner out to pasture and noticed that Jessie's halter was sitting a little weird on her. I take them off in the pasture and when I did there is a plum size lump sitting just above her cheek bone under her eye. It's huge, hot and really hard. Does not seem to cause her any pain however. Now they were out for the afternoons this weekend and have been in the barn for the last three days because of the weather. Could she have hit it hard enough in the barn to cause this? I would think that there would be pain. Gah! She is such a clutz.. It's so easy to tell she is my child.

I'm just wondering if it's a "delayed" reaction to something that she might have done in the pasture... I don't know.

Any Thoughts?

My old horse Jewel had that a few times, she'd get these larger lumps, usually on her shoulders, and best we and the vet could figure, it was a reaction to a certain fly bite. Got hard, and a bit of heat, but no apparent pain. Went away in a few days. :\

A friend had a mare that developed a lump like that in about the same location - turned out to be from an abscessing tooth... Hers became quite large over a few days and burst. Can't remember if they just treated with antibiotics (after it was diagnosed) or if the tooth was pulled...

Jeeezzz... Semi charmed this was supposed to be simple Crap that would have been real quick since the vet was out and checked her in May. He said her teeth were fairly poor but that being on pasture would take the sharper edges off. I'll keep my eyes open for it bursting tho. The thought crossed my mind but I didn't wanna say it out loud. thistle!